1. Field of the Invention
The present invention relates to a manufacturing method for forming a semiconductor structure, and in particular, to a method for forming a semiconductor structure with a more precise critical dimension (CD).
2. Description of the Prior Art
With increasing miniaturization of semiconductor devices, various Multi-gate MOSFET devices have been developed. The Multi-gate MOSFET is advantageous for the following reasons. Manufacturing processes of Multi-gate MOSFET devices can be integrated into traditional logic device processes, and thus are more compatible. In addition, since the three-dimensional structure of the Multi-gate MOSFET increases the overlapping area between the gate and the substrate, the channel region is controlled more effectively. This reduces both the drain-induced barrier lowering (DIBL) effect and the short channel effect. Moreover, as the channel region is longer for the same gate length, the current between the source and the drain is increased.
A multi-gate MOSFET has a gate formed on fin-shaped structures, and the fin-shaped structures are formed on a substrate, wherein the fin-shaped structures formed by etching the substrate are strip structures parallel to each other. With the demands of miniaturization of semiconductor devices, the width of each fin-shaped structure narrows and the spacing between the fin-shaped structures shrinks. Thus, forming fin-shaped structures which can achieve the required demands under the restrictions of miniaturization, physical limitations and various processing parameters becomes an extreme challenge.